Carryover testing

Blank Carryover Test 50 91 Prec-Repeat-Linear ... 

Carryover. Small amounts of analyte may get carried over from the previous injection and contaminate the next sample to be injected [10]. The carryover will affect the accurate quantitation of the subsequent sample. The problem is more serious when a dilute sample is injected after a concentrated sample. To avoid cross-contamination from the preceding sample injection, all the parts in the injector that come into contact with the sample (the injection loop, the injection needle, and the needle seat) have to be cleaned effectively after the injection. The carryover can be evaluated by injecting a blank after a sample that contains a high concentration of analyte. The response of the analyte found in the blank sample expressed as a percentage of the response of the concentrated sample can be used to determine the level of carryover. Caffeine can be used for the system carryover test for assessing the performance of an injector and serves as a common standard for comparing the performance of different injectors. 

We also investigated the tip-wash efficiency using two types of carryover test experiments the first experiment uses source plates filled with pure DMSO and intervening source plates filled with fluorescein solution in DMSO. The measured fluorescein carryover from the source plate of the previous replication cycle to the target plates of the subsequent replication cycle was found to be less than 0.004% (<4 X 10 ). In the second test experiment, six different compound solutions in DMSO were processed on the plate-replication system. The carryover of the compounds from the previous source plate was determined in the target plates of the subsequent replication cycle using LC/MS/MS analytics. The measured compound carryover from the source plate of the previous replication cycle to the target plates of the subsequent replication cycle was always smaller than 0.008% (<8 X 10 ).T... 

The carryover test checks for residual memory effects. Basically, it measures the residual peak area of the target compound in the chromatogram of a blank sample injected immediately after injection of a concentrated solution of the compound (e.g., 1000 mg/L). The carryover effect is evaluated as the percentage of the residual peak area in the blank chromatogram with respect to the peak area of the analyte after the injection of the concentrated solution. Limits of 0.1-0.2% could be considered as acceptable. 

Figure 9 Batch carryover test. The photo in the middle shows the crucibles after the test. Photo on left shows the bottom of the FC AZS crucible. The photo on right shows the bottom of the Vibro-cast AZS crucible.

In principle, the three parts can be taken up in any order without too much interruption in continuity. Within each of the parts there is more carryover from chapter to chapter, so rearranging the sequence of topics within a given part is less convenient. The book contains more material than can be covered in an ordinary course. Chapter 1 plus two of the three parts contain about the right amount of material for one term. In classroom testing the material, I allowed the class to decide—while we worked on Chapter 1—which two of the other parts they wished to cover this worked very well. 

The unique property of quats is the abHity to produce bacteriostasis in very high dilution (Table 6). Because of this abHity, and the carryover of the disinfectant in early test procedures, it was originally thought that these compounds were highly bactericidal. However, for bactericidal action, 10 to 20 times the concentration is required. The quats have a narrower antibacterial spectmm than the phenols, and are much more active against gram-positive... 

The frequency and types of tests employed should, of course, bear some relation to the type of facility being considered. If steam and condensate are not tested, carryover, corrosion, contamination, and other potential problems may be missed, which undoubtedly will have a deleterious impact in other parts of the overall boiler plant. 

Total alkalinity is generally the most relevant alkalinity test, especially in FT boilers where the FW has a low silica content. Testing for T alkalinity provides the best correlation with pH, corrosion inhibition, and tendencies for carryover. 

Testing for steam purity measures the degree of carryover (typically indicated by an increase in electrical conductivity) and provides a starting point for evaluations into specific types of contaminants such as iron, silica, and sodium. 

Pesticides used on crops grown on the test site in previous seasons may also have an impact on the outcome of a field residue trial. Carryover of prior pesticide applications could contaminate samples in a new trial, complicate the growth of the crop in a trial, or cause interference with procedures in the analytical laboratory. For this reason, an accurate history of what has transpired at the potential test site must be obtained before the trial is actually installed. The protocol should identify any chemicals of concern. If questions arise when the history is obtained, they should be reviewed with the Study Director prior to proceeding with the test site. In most annual crop trials, this will not be a significant issue owing to crop rotations in the normal production practices, because the use of short residual pesticides and different chemical classes is often required for each respective crop in the rotation. However, in many perennial crops (tree, vines, alfalfa, etc.) and monoculture row crops (cotton, sugarcane, etc.), the crop pesticide history will play a significant role in trial site selection. 

A complete dose-response analysis was generated for PCP for doses from 0.625 to 20 mg/kg IP (data not shown). PCP exhibited dose-related anticonvulsant action when day one minus day three differ ence scores were compared for all doses tested. When retested with saline only on day five, no reduction in convulsant sever it or super-sensitive response was observed (day one minus day five), indicating no carryover drug effect 48 hours after dosing. At behavioral ly equivalent doses, all compounds assayed were clearly anticonvulsant (table 3). TCP was most potent at the doses tested. PCA was the most efficacious, and reduced convulsant severity by 2.58 points. As with PCP, none of the other phencycli-noids had any carryover effects 48 hours after dosing (day one minus day five). 

Finally, Experiment 28 is used to check for any autosampler/ system sample carryover. A blank water sample is injected immediately following the highest injected volume of the preceding precision/repeatability/linearity test. Any carryover is then calculated as in the procedure described earlier under Autosampler in section (j) of the OQ guidelines. 

It is recommended that OQ test the following on an HPLC system flow accuracy, pump compositional accuracy, pressure pulsations, column oven temperature accuracy/stability, detector noise/drift and wavelength accuracy, autosampler injection precision and carryover. 

The Groton Biosystems protein analyzer tests injection reproducibility at three pressures (e.g., 25mbar at 0.2min, 50mbar at 0.1 min, and lOOmbar at 0.05min). Each injection pressure is injected five times and the complete injection linearity relative standard deviation (RSD) needs to be less than 5%. In addition, the carryover from successive injections is investigated. 

A facility that conducts both GLP-regulated and non-GLP-regulated studies should think carefully about attempting to maintain a dual standard in any one laboratory or with any one group of laboratory workers. In the author s experience, such a dual standard is very difficult to maintain without carryover of non-GLP standards to GLP-regulated work. In such a case it may be far better to maintain a general GLP standard (e.g., data collection, record keeping) for all work in the laboratory, but perhaps allow exceptions for the non-GLP studies in areas such as quality assurance (QA) inspections and analytical requirements for test and control articles and article/carrier mixtures. 

The purpose is to validate the cleaning procedure and ensure that residues of previous product are removed in accordance with the maximum allowable carryover limit calculated, as well as other tests, i.e., visual inspection, pH, conductivity, and TOC. 

For dissolution, both the interrun carryover and the intrarun carryover must be assessed. The interrun carryover, which deals with the carryover from one run to another, can be determined by means of a blank dissolution run that immediately follows an active sample dissolution run. For cumulative carryover, a blank dissolution run would be performed after a series of active sample dissolution runs (minimum of three runs). The intrarun carryover, which deals with the carryover between successive samples in a particular dissolution run, is usually relevant if a common sample pathway is used for all vessels. In this case, a dissolution run with active sample in alternate vessels interspersed with a blank dissolution run (active sample in vessels 1, 3, and 5 and no active sample in vessels 2, 4, and 6) should be tested. A carryover of less than 1.0% of the active concentration in the blank vessels applies. If the carryover observed is higher than the set limit, adjustments to either the flush volume or the vessel wash parameters can be made to eliminate the carryover. 

---